Note: Pro ddi not apply in comments and has to forfeit all rounds to me.

(1) The Moon

Now that humanity knows quite positively that the Moon is not a piece of cheese or a playful god, the phenomena that accompany it (from its monthly cycles to lunar eclipses) are well-explained. It was quite a mystery to the ancient Greeks, though, and in their quest for knowledge, they came up with a few insightful observations that helped humanity figure out the shape of our planet.

Aristotle (who made quite a lot of observations about the spherical nature of the Earth) noticed that during lunar eclipses (when the Earth’s orbit places it directly between the Sun and the Moon, creating a shadow in the process), the shadow on the Moon’s surface is round. This shadow is the Earth’s, and it’s a great clue on the spherical shape of the Earth.

Since the earth is rotating (see the “Foucault Pendulum” experiment for a definite proof, if you are doubtful), the consistent oval-shadow it produces in each and every lunar eclipse proves that the earth is not only round but spherical – absolutely, utterly, beyond a shadow of a doubt not flat.

Refer to the following image from Wikipedia for more details on what happens during a lunar eclipse:

Click for the Original

(2) Ships and the Horizon

If you’ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have, perhaps, noticed a very interesting phenomenon: approaching ships do not just “appear” out of the horizon (like they should have if the world was flat), but rather emerge from beneath the sea.

But – you say – ships do not submerge and rise up again as they approach our view (except in “Pirates of the Caribbean”, but we are hereby assuming that was a fictitious movie). The reason ships appear as if they “emerge from the waves” is because the world is not flat: it’s round.

Imagine an ant walking along the surface of an orange, into your field of view. If you look at the orange “head on”, you will see the ant’s body slowly rising up from the “horizon”, because of the curvature of the Orange. If you would do that experiment with a long road, the effect would have changed: The ant would have slowly ‘materialized’ into view, depending on how sharp your vision is.

(3) Varying Star Constellations

This observation was originally made by Aristotle (384-322 BCE), who declared the Earth was round judging from the different constellations one sees while moving away from the equator.

After returning from a trip to Egypt, Aristotle noted that “there are stars seen in Egypt and [...] Cyprus which are not seen in the northerly regions.” This phenomenon can only be explained with a round surface, and Aristotle continued and claimed that the sphere of the Earth is “of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent.” (De caelo, 298a2-10)

The farther you go from the equator, the farther the ‘known’ constellations go towards the horizon, and are replaced by different stars. This would not have happened if the world was flat:

(4) Shadows and Sticks

If you stick a stick in the [sticky] ground, it will produce a shadow. The shadow moves as time passes (which is the principle for ancient Shadow Clocks). If the world had been flat, then two sticks in different locations would produce the same shadow:

But they don’t. This is because the earth is round, and not flat:

Eratosthenes (276-194 BCE) used this principle to calculate the circumference of the Earth quite accurately. To see this demonstrated, refer to my experiment video about Eratosthenes and the circumference of the earth – “The Earth’s curvature is tasty!“.

(5) Seeing Farther from Higher

Standing in a flat plateau, you look ahead of you towards the horizon. You strain your eyes, then take out your favorite binoculars and stare through them, as far as your eyes (with the help of the binocular lenses) can see.

Then, you climb up the closest tree – the higher the better, just be careful not to drop those binoculars and break their lenses. You then look again, strain your eyes, stare through the binoculars out to the horizon.

The higher up you are the farther you will see. Usually, we tend to relate this to Earthly obstacles, like the fact we have houses or other trees obstructing our vision on the ground, and climbing upwards we have a clear view, but that’s not the true reason. Even if you would have a completely clear plateau with no obstacles between you and the horizon, you would see much farther from greater height than you would on the ground.

This phenomena is caused by the curvature of the Earth as well, and would not happen if the Earth was flat:

(6) Ride a Plane

If you’ve ever taken a trip out of the country, specifically long-destination trips, you could notice two interesting facts about planes and the Earth:

Planes can travel in a relatively straight line a very long time and not fall off any edges. They can also, theoretically (and some do, though with stops along the way), circle the earth.Correction (Courtesy of Klaynos, from scienceforums.net): Apparently, planes can circle the Earth without stopping!

If you look out the window on a trans-Atlantic flight, you can, most of the times, see the curvature of the earth in the horizon. The best view of the curvature used to be on the Concorde, but that plane’s long gone. I can’t wait seeing the pictures from the new plane by “Virgin Galactic” – the horizon should look absolutely curved, as it actually is from a distance.

(A picture of the curved horizon from a Concorde plane can be seen here).

(7) Look at Other Planets

The Earth is different from other planets, that much is true. After all, we have life, and we haven’t found any other planets with life (yet). However, there are certain characteristics all planets have, and it will be quite logical to assume that if all planets behave a certain way, or show certain characteristics – specifically if those planets are in different places or were created under different circumstances – our planet is the same.

In other words: If so many planets that were created in different locations and under different circumstances show the same property, it’s likely that our own planet has the same property as well. All of our observations show planets are spherical (and since we know how they’re created, it’s also obvious why they are taking this shape). Unless we have a very good reason to think otherwise (which we don’t), our planet is very likely the same.

In 1610, Galileo Galilei observed the moons of Jupiter rotating around it (click here to see a beautiful video reconstruction of his observations). He described them as small planets orbiting a larger planet – a description (and observation) that was very difficult for the church to accept as it followed a geocentric model where everything was supposed to revolve around the Earth. This observation also showed that the planets (Jupiter, Neptune, and later Venus was observed too) are all spherical, and all orbit the sun.

A flat planet (ours or any other planet) would be such an incredible observation that it would pretty much go against everything we know about how planets form and behave. It would not only change everything we know about planet formation, but also about star formation (as our sun would have to behave quite differently to accustom a “flat earth” theory), what we know of speeds and movements in space (like planets orbits, and the effects of gravity, etc). In short, we don’t just suspect that our planet is spherical. We know it.

(8) The Existence of Timezones

The time in New York, at the moment these words are written, is 12:00pm. The sun is in the middle of the sky (though it’s hard to see with the current cloud coverage). In Beijing, where Michael Phelps is likely getting ready for yet another gold medal, it’s 12:00am, midnight, and the sun is nowhere to be found.

In Adelaide, Australia, it is 1:30am. More than 13 hours ahead. There, the sunset is long gone – so much so, that it’s soon going to rise up again in the beginning of a new day. Here’s a list showing what time it is around the world when it is 12:00pm in New York city.

This can only be explained if the world is round, and rotating around its own axis. At a certain point when the sun is shining on one part of the Earth, the opposite side is dark, and vise versa. That allows for time differences and timezones, specifically ones that are larger than 12 hours.

Another point concerning timezones, the sun and flat/spherical Earth: If the sun was a “spotlight” (very directionally located so that light only shines on a specific location) and the world was flat, we would have seen the sun even if it didn’t shine on top of us (as you can see in the drawing below). The same way you can see the light coming out of a spotlight on a stage in the theater, even though you – the crowd – are in the dark. The only way to create two distinctly separate timezones, where there is complete darkness in one while there’s light in the other, is if the world is spherical.

(9) The Center of Gravity

There’s an interesting fact about mass: it attracts things to it. The force of attraction (gravity) between two objects depends on their mass and the distance between them. Simply said, gravity will pull toward the center of mass of the objects. To find the center of mass, you have to examine the object.

Consider a sphere. Since a sphere has a consistent shape, no matter where on it you stand, you have exactly the same amount of sphere under you. Imagine an ant (perhaps the same one from the previous point) walking around on a crystal ball. Assuming the crystal ball is polished, the ant’s only indication of movement would be the fact it’s moving its feet. The scenery (and shape of the surface) would not change at all.

This is a simple debate question (as constructed by you)Your position is that the world is 'not flat'.You introduce high school science to our debate in your second post. I will not get into this, nor will I move our discussion to degree level. You attempt to establish a 'spherical' noun/adjective to the earth's general demeanour without conviction. You speak about spherical gravity when any basic understanding of the earth's composition will dismiss these notions as quaint. Try and get your head around the workings of modern GPS systems and elevation to understand that we cannot ever know enough in these fields. Consider the approaches of Newton and Einstein towards explanations on gravitational phenomena and you may be less willing to introduce simplistic notions of this everday characteristic of Earth into your debate strategies in future. Consider the concept of a geoid model of earth elevation if you like. What the polished sphere mentioned in your post has to do with our discussion about the Earth's 'not flatness' is beyond me?

Let's get back to the Basics that were introduced by you.

Your :Definitions

Earth:the planet on which we live

Flat:having a smooth, level, or even surface : not having curves or bumps--------------------------------------------------------------------------------------------------------------

We will not differentiate between components of 'Earth' for this debate. We will allow the steam locomotive merge with the smoke. I will not mention oceans or atmosphere. I will use your phrase 'Earth' ie the planet on which we live.

Your assertion that the earth is 'not flat ' rests on the earth having a 'non smooth', 'not level', and uneven surface. What tolerances would you apply to this adjectival approach to science. Surely, you will not become mathematical in our examination of this three dimensional celestial entity. Surely you will not attempt to approximate this 'thing' with conceptual logarithms. You are correct in this. Let's finish as we started here, ie within a real discussion.

A question for you: Is the Earth as 'flat as a pancake'? I think it is.If there are crumbs on a table, is it still flat?If there is an indentation in the table due to negligence, then is it still flat. What are your tolerances in this?Is Estonia flat? I think it is, and I will explain why. I have been to Estonia, it is a relatively small European country that is criss-crossed by long straight roads.

Now I want you to try and forget all the topographical map presentations that you have ever seen and I want you to do some maths for me. Let's make a scale model of Estonia in a small car port that is 10M squared in area. I want to place this 'Big Egg Mountain' thing on my map in accurate 3D scale. How high will it be on the map? You tell me.

Now make a scale model of Estonia on a standard NFL pitch. Would a player trip on this 'Big Egg' or would the map appear as a level flat playing field. You could place a scale model of the earth's surface area into the same car port. What height do you imagine that MT Everest would achieve if accurately represented to scale on this map. Would it bust your car sump. Would it burst your tyre, like a nail. Would it be almost/totally indescernable when compared to the flat car port. You have work to do here. I know the answer. Again I must ask what your tolerances are when using the noun/adjective 'flat. You tell me.

The Baltic sea is 'flat'.Estonia is flat.The Earth is flat.

To think otherwise within this simple debate is to be 'incorrect' ie not correct.

You had no permission to accept this debate. Also you did not follow the structure.

This debate is impossible to accept please apply in comments. If you accept you forfeit all points to me.

Structure

1. Con acceptance, Pro writes Contentions

2. Con writes Contentions, Pro rebuts

3. Con rebuts, Pro makes conclusion

4. Con makes conclusion, Pro waives

I will write my arguments again.

Also my arguments were not from a high school place.

Now that we have access to space, the easiest way to prove the Earth is spherical is to leave it and view it from a distance. Astronauts and space probes have done just that. Every picture of Earth ever taken shows only a circular shape, and the only geometric solid which looks like a circle from any direction is a sphere.

One of the oldest proofs of the Earth's shape, however, can be seen from the ground and occurs during every lunar eclipse. The geometry of a lunar eclipse has been known since ancient Greece. When a full Moon occurs in the plane of Earth's orbit, the Moon slowly moves through Earth's shadow. Every time that shadow is seen, its edge is round. Once again, the only solid that always projects a round shadow is a sphere.

This is a question that has been asked for many years, and there are some very intuitive, and some not-so-intuitive answers.

To start with... there's a horizon, meaning that the surface that one is observing from is not an infinite plane. On the clearest of days, the only restriction to one's range of sight is the horizon. There can be two explanations for this - one, that the Earth at some point just stops, as if you were looking off the edge of a table. The other is that the Earth is round. Hundreds of years ago, before the invention of the compass or sextant, precise navigation for ships was difficult, even with the stars. Ships that ventured past sight of land were often lost, and thus it was generally believed that the world simply *stopped* at the end of the horizon. With the invention of the compass, and improved map-making, people began to dare more, and with the return of Columbus from his trans-Atlantic voyage, the concept of the Earth as flat was shattered.

Further proof of the Earth being round came after the voyage of Columbus. When Newton discovered and measured the force of gravity, that number could then be tested anywhere the theory was known. Since the force of gravity is roughly the same everywhere on the globe, it could be surmised that the Earth must be spherical. If the Earth were not round, whole hemispheres would have different atmospheric pressure and significantly different sea levels. Also, pictures taken of the Earth in the last 50 years have proved absolutely conclusively that the Earth is round. These are just the arguments that don't require much physics knowledge to explain, there are others that are more technical, but I think that the simplest arguments are the best.

There are a multitude of methods in which any one can prove that the earth is a sphere. These are the most common.

You can launch a rocket to a high altitude and take pictures of the earth (which various government agencies and private groups have already done thousands of times in the past), but that isn't the most practical way. Pictures and videos taken by orbiting satellites and space stations are certainly the most definitive proof that the earth is a sphere.

But if you're not convinced, read on...

You can also observe, with binoculars, ships slowly 'sinking' below the horizon as it sails farther and farther out to the ocean, then watch them come back. They certainly didn't fall off the edge of the earth! You can also sail or fly around the world.

The Greeks discovered that the earth is round by observing lunar eclipses (i.e. when the earth blocks the sun from the moon, casting its round shadow on the moon's surface).

Another method is simultaneously measuring the length of the shadows cast by identical poles perpendicular to a flat surface that is tangential to the earth's radius at various, distant locations. If indeed the earth is round, then the shadows should all vary in length from one distant location to another, which means that the angle at which the parallel rays of sunlight struck each pole varied from one location to another. (recall the alternate-angles theorem from Geometry class) If the earth is flat, then the lengths of all the shadows should be identical when measured simultaneously, since all rays of sunlight that strike the earth are parallel. However, they are not identical, but in fact, varies in such a way that the angles indicate a spherical surface. (This was one of the earliest methods to determine the radius of the earth)

Also, keep in mind the 24 hour time zones. When it is noon in Hawaii, it is approximately midnight in the Middle East and vice versa. How can it be noon and midnight simultaneously? It is certainly impossible with a flat earth and a sun millions of times more massive.

If I were a billionaire and physically fit, then proving to you the earth is round would be no problem. I can just take you with me on the space shuttle and we'll watch with our own eyes the earth from the orbiting International Space Station.

Rebuttal

Even though Estonia is flat doesn’t mean that Earth is flat. You gave no explanation to say why Earth was as flat as a pancake. Also you told the voters and I to do the math when you are supposed to do it

You gave no supportment in your arguments. You told no explanation and had no meat in your argument. You just told us to do everything

Your position is supposed to proceed along the line....the Earth is not Flat. You insist on emphasising the 'spherical' nature of the Earth. You should start a new debate topic on this subject. You would probably find it hard to attach a 'spherical' label to the earth in any real way. That is another debate. Personally, I wish to conclude the debate in hand. I will again use your definitions for this purpose.

Your Definitions

Earth:the planet on which we live

Flat:having a smooth, level, or even surface : not having curves or bumps

---------------------------------

I have repeatedly requested information regarding your tolerances with regard to the adjectival notion of 'flat'. Unfortunately the exercise offered to you in this regard was spurned. You now want to change the subject. Look at your definition above ..........smooth, level, even , curves, bumps. These are subjective notions at best and simple in the extreme. Let me attempt to help you in this regard.

'Imagine the subjective notion of tall'

A six foot man is regarded as tall in most demographics but if he plays for a professional basketball team he would be regarded as small. The average height in the NBA is 6'7'.

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This is what a piece of paper looks like under a microscope.Is it flat? Is it smooth? Has it bumps? You can see for yourself.

Flat, as defined by you is what the world is. All our perceptions require 'flatness' we work off 'flatness' to describe anomalies. There is much more that could be said about this, ie the distortion within human sight along the vertical axis. etc etc.

I am not here to inform. I am here to win this debate with you.

A sheet of paper on a horizontal table is 'flat'. I assume that you agree, yet, it's surface contains more variation than Estonia or indeed our Earth. They are therefore 'flat' by reference to your definitions of same. I will allow you to conclude and then waive graciously to adhere to your protocol.

Again, you did not support your argument. Also if you don't inform the voters about your side you will lose. If you don't inform= you lose. Do you think master debaters can win debates by no supporting there side?

Why I won this debate

I won this debate because many reasons. I had good arguments and rebutted well. Pro did not have any information and supported his side which means he loses. You have to inform the voters and convince them to win a debate, not just tell the voters to make their own argments and vote for you.

Thank You debate-master1 for your participation here.I wil leave the second last word to Jonbonbon

Posted by Jonbonbon 2 days ago

Just argue that what we see isn't necessarily true because perceptions can trick us (like at night when part of the road looks like it doesn't exist, or when it's hot and the same effect occurs). None of our senses are truly reliable, therefore there is not way for us to prove that the earth is round, and since it makes sense that when we walk it doesn't feel like we're walking around a big ball, the earth is probably flat with portals on all sides to send us to the opposite side so we don't fall off and die.

The Earth is flat because we experience our existence as such. There is a vertical plumb-line suspended over every point on the earth and there is a perpendicular flat line to match at its base. There is 'flat' everywhere and it has parallels that are flat at every elevation. Our perceptions and our understandings require this and that is why our attempts at self-reference require this zero/negative/plus diagram of surface that gravitates us towards safety and ease. All life on this earth uses this. We are tactical when we deal with situations that are 'off-flat'. It is often a matter of survival to accurately access the variation.

I will leave you , debate-master1, to consider the origins of words such as the ones you chose for this debate, ie flat, bump, etc and I will add a couple to the mix, ie variation, level. We can both share the word ' smooth'.

The question here is are we talking to the shape of planet Earth or about the smoothness of its surface and if we are talking about smoothness of its surface, in what scale we should analyze this. Because if we would shrink down the planet Earth to the size of a cue ball, it would be smoothest cue ball ever made.

which position are you elaborating on, ' being a sphere or being spherical in nature' Surely you cannot apply the absolutes of an abstract perfect sphere to all things that are 'spherical' in nature. The earth is not a sphere. You can debate this if you like but you will most likely be defeated.

Definition of sphere: "A sphere has a single curved surface. A sphere contains no flat spots." Con has successfully given a lot of evidence on how the Earth has a spherical shape, and as indicated a sphere has no flat spots, meaning that Con is correct.

However, the majority of Con's evidence were literally copy-pasted, which is plagiarism 100%. Pro also failed to read the first 2 sentence of the debate which damages credibility.